Sound absorbing material and process for making same



COMPOSITIONS,

COATING OR PLASTIC. W

June 20, 1933. c. BIRCHY ET AL SOUND ABSORBING IATERIAL AND PROCESS FOR mumm sum Filed Sept. 9, 1931 6 pa 02:4/ dam/e72 COMPOSITIONS, COATING OR PLASTIC.

Patented June 20, 1933 UNITED STATES Examine:

PATENT OFFICE CHARLES IBIRCHY AND OSWALD ROBERT IBIRCHY, OF ATLANTA, GEORGIA, ASSIGNORS OF ONE-HALF TO SAMUEL D. HEWLETT, 0F ATLANTA, GEORGIA SOUND ABSORIBING MATERIAL AND PROCESS FOR MAKING SAME Application filed September 9, 1931.

Generically this invention relates to a structural material but it is more especially directed to the type having sound absorbent properties and process of making same.

One of the principal objects of this invention is the provision of a material having acoustical properties, which material may be used for manufacturing sound absorbing stone, tile, and plaster for walls, ceilings, and the like, and without the use of any additional binding material.

Another important object of thls invention is the provision of a sound absorbent material for walls and ceilings, for halls, auditoriums, theaters, hotels, oflice buildings, and the like, composed of particles of a single body substance united at their points of contact by the inherent properties .of said particles, and adapted to absorb sounds in excess of 35 per cent.

A further important object of this invention is the provision of a sound absorbent material consisting of particles formed from a body substance and bonded together at their limited points of contact by the inherent properties of said substance, const1- tu ting an integral porous sound absorbing material.

Still another object of this invention is the provision of a sound absorbent material for walls, ceilings, and the like, formed from particles of a plastic substance united at their points of contact by the inherent properties of said particles, constituting a porous material having acoustical properties, and formed with a perforated backing.

With these and other objects in view which will become apparent as the description proceeds, the invention resides in the construction, combination and arrangement of parts, hereinafter more fully described and claimed, and illustrated in the accompanying drawing, in which the characters of reference indicate like parts throughout the several figures, of which:

Fig. 1 is an exaggerated sectional View of our improved sound absorbing material and perforated backing united therewith; and

Fig. 2 is a similar view of the acoustical Serial No. 561,922.

material, one surface of which is formed with a plurality of perforations.

The acoustical materials of this general character with which we are familiar have proven deficient and unsatisfactory by requiring much time and labor to produce and necessitating a number of ingredients, thereby rendering the production of such material costly, and further deficient in being incapable of sustaining a heavy load pressure, and it was to overcome such disadvantages by providing a sound absorbent material and process of making same comprising a masonry product pleasing to the eye, a fire resistant, capable of sustaining heavy load pressure, consisting of a single material formed into particles molded into the desired form, the inherent properties of the particles themselves uniting them at their points of contact into a porous sound absorbent material at a great saving in cost,

time, labor and material, that we provided I proved acoustical material A, composed of particles 1 of a suitable cementitious substance of varying shapes bonded or united at their points 0 contact as at 2 by the inherent properties of such particles forming a plurality or myriad of intercommunicating channels 3 openly penetrating the surfaces of said material, thereby forming a cellular or porous product adapted to absorb in excess of 35 per centum of sounds, said material being preferably formed with a backing B of concrete or any suitable material cementitiously or otherwise united with the rear surface of said material A, and formed with a plurality of perforations 4 communicating with the intercommunicating pores 3 through which sounds may pass therefrom.

In many instances practice has demonstrated the desirability of omitting the backing B and forming the perforations 4 directly in the material A as clearly shown ed as 4a. The material as above described is adapted to be applied to walls or ceilings indicated as C, preferably with a space 5 between the material and the wall, the exposed surface 6 of material A constituting the exposed wall surface when the application of such sound absorbent or acoustical material has been made.

The method and material used in the manufacture of our improved acoustical material or wall structure is as follows: A quantity of cement is mixed with water to such a consistency that it can be formed into a mass or wads of convenient size. The mass or wads are then permitted to become firm enou h to handle and then passed through suitable screens or machines in the form of shred-like particles of varying lengths, the mass of such particles then being lightly pressed into molds of the desired sizes and shapes 'ust before the setting of the cement takes place, such particles of cement, being still active, bind themselves together where they come in contact with each other, and when the cementitious body becomes set, form an integral porous structure constituting many intercommunicating channels through which sound may pass, and when completely set a wall surface structure is presented of great strength and durability and having sound absorbing properties in excess of 35 per centum.

\Vhile in process of molding certa.in of the particles 1 may lose their shred-like form, a great number will remam lntact, so that the porosity will be much more irregular than if the particles were of a uniform size, thereby tending to further develop the acoustical properties of the finished product.

\Vhen it is desired to apply the backing B to the acoustical material A the concrete or other material forming such backing is applied to the rear surface of the material A while it is still in the mold and before it has completely set, whereby such materials are joined by the cementitious properties of the acoustical material or of both materials, depending upon the properties of the backing material, also where the backing material likewise has cementitious properties it may be subsequently applied to the material A, as will be clear without further description. At the time the backing A is applied and while in a plastic state a plurality of sticks are inserted through said backing material or body material and subsequently are removed to form the perforations 4, or 4a, or said perforations may be formed in any suitable manner.

\Vhile we have preferably designated concrete we are not limiting ourselves to any particular material or type of backing since any suitable material or type of backing may be employed, depending upon the exigencies of the particular requirements.

It is, of course, to be understood that the size and shape of the particles and size and irregular contours of the consequent intercommunicating interstices therebetween may be varied to change the degree of sound absorption in accordance with the particular acoustical requirements, as desired.

From the above it will be apparent that we have eliminated the use of any additional binding media for bonding the particles at their points of contact, have greatly reduced the cost of production by constructing our improved acoustical material from a single substance having cementitious properties, eliminating unnecessary steps in method of production, and, with all, have produced a durable material adapted to effect a maximum of sound absorption, which may be constructed at points remote and delivered to location or which may be initially formed in place as desired.

Although in practice we have found that the form of our invention illustrated in the accompanying drawing and referred to in the above description as the preferred embodiment is the most efiicient and practical; yet realizing the conditions concurrent with the adoption of our invention will necessarily vary, we desire to emphasize that various minor changes in method, details of construction, proportion and arrangement of parts, may be resorted to within the scope of the appended claims without departing from or sacrificing any of the principles of this invention.

Having thus described our invention, what we desire protected by Letters Patent is as set forth in the following claims:

1. A method of producing a sound absorbing material consisting in forming a material into a plastic substance, then separating the substance into particles, said particles embodying a single substance and uniting under pressure the particles at their points of contact by the inherent properties of said particles into a cellular sound absorbent material of the same molecular construction throughout.

2. A method of producing a sound absorbing material consisting in reducing a single cementitious substance to a plastic, separating said plastic into particles, forming the mass of particles by pressure into the desired shape while the cementitious properties are still active, said properties uniting the particles at points of contact into an integral mass in the form of a porous sound absorbent material of the same molecular construction throughout.

3. A method of producing sound absorbingmaterial of the character described cons sting in forming a substance having cementitious properties into a plastic, permitting COMPOSITIONS, COATING OR PLASTIC.

said plastic to partially set, then grating said material into shred-like particles, molding said particles into the desired form, uniting said particles at their points of contact by said cementitious properties to form a sound absorbent material of irregular porosity, and applying a backing to said material.

4. A method of producing sound absorbing material of the character described consisting in forming a substance having cementitious properties into a plastic, permitting said plastic to partially set, then grating said material into shred-like particles, molding said particles into the desired form, thereby uniting said particles at their points of contact by said cementitious properties to form a sound absorbent material having perforations communicating with said pores.

5. A method of producing a sound absorbing material consisting in forming a single exclusively cementitious substance into a semi-plastic, separatin said plastic into irregular shaped partic es and before they have completely set -moulding the mass into the desired form, uniting the particles at their points of contact by the inherent properties of said particles in the form of a cellular sound absorbing material of the same molecular construction throughout, and applying a perforated backing to said material.

6. A method of producing a sound absorbing material consisting in forming a single wholly cementitious substance into a semi-plastic, separating said plastic into irregular shaped particles and before they have completely set, pressing them in a mold, uniting the particles at their points )f contact by the inherent properties of said particles in the form of a cellular sound absorbing material of the same molecular construction throughout, and forming a plurality of perforations in one surface of said :naterial.

7. A method of producing a sound absorbing material consisting in forming a single wholly cementitious substance into a semi-plastic, reducing said plastic mass to particles having irregular dimensions, and before they have completely set molding said mass of particles into the desired shape, uniting the particles at their points of contact by their inherent properties un- "ler normal atmospheric conditions in the form of a porous sound absorbing material of the same molecular construction throughout.

8. A method of producing a sound ab- "orbing material consisting in forming a single wholly cementitious substance into a semi-plastic, reducing said plastic mass to particles having irregular dimensions, and before they have completely set pressing said mass of particles into intimate rela- This specification signed this 5th day ofQ September, A. D. 1931.

CHARLES BIRCHY. OSWALD ROBERT BIRCHY. 

